This invention relates to voltage regulating apparatus for variable speed permanent magnet alternating current generators.
Voltage regulator systems for permanent magnet alternating current generators are known, examples being the systems disclosed in the U.S. Pat. Nos: 3,443,197; 3,369,170; 3,427,529. In the systems of these patents the output or stator winding of a permanent magnet alternator is connected to a bridge rectifier that is comprised of controlled rectifiers and diodes. By turning the controlled rectifiers on and off as a function of the output voltage of the bridge rectifier, the direct output voltage of the bridge rectifier is maintained substantially constant.
One of the problems associated with the systems of the type disclosed in the above referenced patents is that the systems have high copper losses in the stator winding and poor power factor at high rotor speeds.
A voltage regulating circuit for a variable speed permanent magnet alternating current generator which reduces the copper loss in the stator or output winding of the generator and improves the power factor at high rotor speeds has been disclosed in U.S. Pat. No. 5,214,371 assigned to the assignee of the present invention. In that circuit, a stator or output winding is comprised of two sets of windings. The first winding set has a larger number of turns than the second winding set. The first winding set is connected to a first bridge rectifier that has a plurality of controlled rectifiers, and the second winding set is connected to a second bridge rectifier that has a plurality of controlled rectifiers. The system is arranged to enable the first bridge rectifier and disable the second bridge rectifier when the speed of the rotor of the generator is below a predetermined speed. At rotor speeds above the predetermined speed, the second bridge rectifier is enabled and the first bridge rectified is disabled. Both bridge rectifiers feed a direct voltage load which may be the battery or other loads in a motor vehicle electrical system. The output voltage of the bridge rectifiers is sensed and the system controls the conduction angle of the controlled rectifiers as a function of the sensed bridge rectifier output voltage to maintain the output voltage of the bridge rectifier that is enabled substantially constant.
While the advances embodied in the circuit of U.S. Pat. 5,214,371 as outlined are significant, some improvements, particularly with respect to circuit complexity and component parts proliferation are desirable.